Room-temperature electroluminescence from tensile strained double-heterojunction Germanium pin LEDs on Silicon substrates

In this work, electroluminescence from the intrinsic Germanium layer of tensile strained Germanium LEDs is observed at room temperature. The pin LEDs are fabricated by low temperature molecular beam epitaxy with a double-heterojunction process on Silicon substrates. The tensile strain is adjusted at 0.24% with an annealing step at 700 °C leading to a lowering of the direct band gap. Electroluminescence spectra show a value of 0.781 eV for the direct band gap or an infrared shift of 19 meV. Increasing of the intrinsic layer thickness leads to higher electroluminescence intensity.

► Electroluminescence in tensile strained Germanium LEDs is observed at room temperature. ► The LEDs are fabricated by low-temperature MBE using a double-heterojunction design. ► Tensile strain values of 0.24% are achieved after annealing at 700 °C. ► The electroluminescence spectra show direct band gap value of 0.781 eV.